Help with material for pants

Perhaps some folks here can help me with a problem I'm having locating
some items I need.

Here is my problem, we are issued uniform pants and they must be dry
cleaned.  Now after some time the dry cleaning has worn the rubber out
that helps hold your shirt inside. This rubber is inside the waist
band and is gone.  What this does is keep you having to do a re-tuck
all day and it gets old fast.

I have been to very fabric store between in our area.  No one carries
this stuff.  Years ago I had the same problem and I was able to find
some a fabric store.

The last store I was at the lady said she had not seen this stuff in
years.  I'm looking for a supplier where I can buy a roll and keep it
on hand.  The sad thing is the pants are in good shape it's only the
waist band that is shot.

Any help would be appreciated